1. Field of the Invention
The present invention relates to a collator or sorter for distributing and sorting various types of paper sheets for photocopiers and printers and, more particularly, to a collator which is capable of easily detecting the amount of sheets stacked on a plurality of bins, that is, detecting whether the bin is empty or whether the bin is full and under the overflow condition; and which is also capable of other functions.
2. Description of the Prior Art
According to the conventional method for discriminating empty or full bins in a collator of the type described above, the amount of stacked sheets is detected through the weight of the sheets stacked on the bin. However, with this method, in case the sheet is curled, or the like, and the full bin condition is reached with a small number of sheets stacked on the bin, the full bin condition cannot be detected. In addition, it is difficult to detect the weight of one sheet, so that detection of an empty bin condition is difficult. The conventional collator of this type is thus defective in stability and reliability.
Another conventional collator has also been proposed which incorporates light-emitting elements and light-receiving elements (photosensitive elements) arranged in each of a plurality of bins for discriminating between the empty bin or the full bin. However, the collator of this type becomes complex in structure and requires a larger space. Moreover, since the light-emitting elements and the photosensitive elements must be arranged close to each other, noise of the light source tends to be introduced into the photosensitive elements and the reliability is thus degrated.
The inner wall of the bin inlet of the conventional sorter or the like is straight. Therefore, sheets stacked on the bin may float through the sheet outlet because of a breeze, vibrations, impacts or the like, thus sealing the bin inlet. This may interfere with insertion of the next sheet or erratic detection of the overflow condition when the bin is, in fact, not full.
With a collator of this type, a measure is taken to detect the full condition for sheets inserted in one of a plurality of bins and to stop insertion of the sheets in the bin or transfer to another bin. However, with a recent high-speed printer or the like, when a full bin is detected, another sheet cannot be stacked, or some additional sheets may be stacked but others which have been printed by high-speed printing cannot be stacked any more. For this reason, printing must be started after confirming that the printed sheets may all be stacked on the bin. This significantly slows down the speed of the printer.